RNA viruses can be classified according to the sense or polarity of their RNA into negative-sense (−) and positive-sense (+) RNA viruses. The largest family of viruses is the single stranded negative-sense (−) RNA (“ssRNA”) family of viruses. Their viral RNA genome cannot be directly translated, instead the (−) strand is complementary to the viral mRNAs that need to be produced and translated into viral proteins. At the time of this disclosure, one order and eight families are recognized in this group. There are also a number of unassigned species and genera:
Order Mononegavirales                Family Bornaviridae—Borna disease virus        Family Filoviridae—includes Ebola virus, Marburg virus        Family Paramyxoviridae—includes Measles virus, Mumps virus, Nipah virus, Hendra virus, RespiratorySyncytial Virus (RSV), and Newcastle Disease Virus (NDV)        Family Rhabdoviridae—includes Rabies virus        Family Nyamiviridae—includes Nyavirus        
Unassigned families:                Family Arenaviridae—includes Lassa virus        Family Bunyaviridae—includes Hantavirus, Crimean-Congo hemorrhagic fever        Family Ophioviridae        Family Orthomyxoviridae—includes Influenza viruses        
Unassigned genera:                Genus Deltavirus—includes Hepatitis D virus        Genus Dichorhavirus        Genus Emaravirus        Genus Nyavirus—includes Nyamanini and Midway viruses        Genus Tenuivirus        Genus Varicosavirus        
Unassigned species:                Taastrup virus        Sclerotinia sclerotiorum negative-stranded RNA virus 1        
Despite decades of efforts by researchers to develop an effective, approved, and available filovirus treatment for individuals, currently there are no United States Food and Drug Administration-approved vaccines or therapeutics for treatment of infection with filovirus diseases.